strcmp returns unexpected value in C

Question

I'm new to C, I have lines of code look like this:

char user[16];
fgets(user,16,stdin);

I typed "zeyang" on the keyboard, and I have another code:

char pwname[1000];
pwname="zeyang";

Then I use strcmp to compare user and pwname:

strcmp(user, pwname);

The return value is a negative number, I expect it to be 0, because they are all "zeyang". Why it isn't 0?

Answer 1

fgets includes the typed newline if there's room. You're comparing "zeyang\\n" with "zeyang" . From the fgets(3) man page :

The newline, if any, is retained.

Answer 2

来自stdin的第一个字符串包含一个附加的换行符。

Answer 3

The problem is that the sentence you enter will be terminated by a new line character. (I guess you pressed ENTER when you have finished to insert characters. :D

In this case I would use strncmp :

strncmp(user,pwname,strlen(pwname)); 

This code won't compare the new line character.